Excitatory amino acid receptors mediate slow synaptic transmission in turtle cerebellum

Abstract

In the isolated turtle cerebellum intracellular recordings from Purkinje cell dendrites and somata reveal novel slow excitatory synaptic potentials evoked by activation of climbing fiber (CF) or parallel fiber (PF) inputs. Classical fast excitatory synaptic responses to CF and PF stimulation are followed by large, slow excitatory postsynaptic potentials (sEPSPs) which are associated with an increase in conductance and are enhanced by hyperpolarization. Both sEPSPs are blocked by the excitatory amino acid (EAA) antagonist kynurenate, but not by dl-2-amino-5-phosphonovalerate (AP-5). The EAA receptor antagonist l-amino-4-phosphonobutyric acid ( l-AP-4) reversibly blocked the PF-sEPSP without affecting the CF-sEPSP. Two novel slow synaptic potentials mediated by excitatory amino acid receptors can therefore be observed in turtle cerebellum which may play an important role in synaptic integration.